On an Independence Day which saw nine Americans take to court in the Wimbledon singles, Michael Hincks ponders who will fly the Star-Spangled Banner once the Williams sisters retire.

Serena and Venus Williams were once more the two leading American attractions on the Fourth of July, producing firework en route to the Wimbledon third round.

First up was Venus on Court One, with the 38-year-old recovering from losing the first set 6-4 to Alexandra Dulgheru by winning the next two 6-0 6-1.

The five-time champion continues to defy both logic and those aged a decade or so younger, and having fought back from a set down in her opening two matches, it is evident she is displaying the same tenacity that saw her reach the final 12 months ago.

The five-time winner finds herself in the same half of the draw as sister Serena, ruling out the possibility of a 10th Grand Slam final between the two, though it does mean a semi-final meeting is on the cards.

Questions will linger over Serena’s fitness as to whether she can get that far, but there was no need to exert too much energy against Viktoriya Tomova on Centre Court, with the 36-year-old wrapping up a swift 6-1 6-4 victory in just 66 minutes.

Who next after the Williams retire?

There is no saying how much longer Venus and Serena will remain on Tour.

Serena joked on Tuesday that she will play for as long as Roger Federer does, while the fact she is one behind Margaret Court’s Grand Slam singles record of 24 has many believing it could be 25 then out.

How long that takes obviously remains unknown. It’s no mean feat making it through a two-week championship, even if there is the sense she does not have to be at 100 per cent to go all the way.

And with each tournament comes the added challenge from younger players coming through, and those on the periphery of Grand Slam success finally rising to the level that sees them claim a maiden major.

In that stead, two Americans are leading the way. Sloane Stephens, 25, may have exited Wimbledon in the first round, but the world No 4 followed up US Open glory last year with a run to the French Open final last month.

There is a frustrating inconsistency to her game – having also lost in the Australian Open first round in January – but overcoming five seeded players en route to claiming her maiden Grand Slam proved she is ready to take the baton from the Williams’.

Then there is Madison Keys, the losing finalist last September, while she lost to her compatriot once more in the French Open semis.

Bitter defeats for the 23-year-old to swallow, but the fact she reached the Australian Open quarter-finals highlighted how she is starting to put together an impressive string of Grand Slam performances.

Keys was the first of three Americans on Court 12 on Wednesday, and she continued her charge for a maiden major in impressive fashion when dismissing Luksika Kumkhum 6-4 6-3.

Evgeniya Rodina awaits in the third round, and in the absence of Stephens, she now has the opportunity to prove that American hopes can be placed onto her shoulders as well, though to do so here at Wimbledon, there is every chance she will have to beat Serena in the fourth round – a potential match-up not to be missed.

Can Isner or Querrey challenge?

Following Keys on Court 12 was the familiar sight of ace machine Sam Querrey, who saw off Serhiy Stakhovsky in straight sets, while John Isner was the third American to grace the same grass on Wednesday, with his match against Ruben Bemelmans heading to a decider after he squandered a two-set lead.

With Querrey seeded 11th, and Isner ninth, they have every chance of serving their way deep into the second week at Wimbledon, but both still remain firm outsiders for the title.

Querrey enjoys the grass courts, having reached last year’s semi-finals, and will likely have to beat Federer in the quarters if he wants to make his dreams of a first Grand Slam final become a reality.

Meanwhile, Isner has not taken so kindly to the green of SW19, having never progressed beyond the third round.

The pair have been the US' main hopes in the men’s singles since Andy Roddick retired, but in terms of Grand Slam prospects, they are now being overshadowed by the younger crop coming through.

Much is expected from Frances Tiafoe and Taylor Fritz, with both 20-year-olds in second-round action on Thursday, while Jared Donaldson, 21, is another hoping to break through, and he found himself locked in a battle in the fading light against promising Greek 19-year-old Stefanos Tsitsipas.

The trio are all ranked in the top 70, and Tiafoe (52), Donaldson (54) and Fritz (68) are all destined to continue climbing the ladder and one day usurp Isner and Querrey.

The hope will be that they rise to the very top. There hasn’t been an American men’s champion in a Grand Slam since Roddick won the US in 2003, while the Pete Sampras and Andre Agassi era also came to its conclusion 15 years ago.

And though it will seemingly be a few years before the men catch up with their female compatriots, the future remains bright for the nation celebrating its 242nd birthday.

We may not have to wait much longer before the Americans are dominating the final weekends of Grand Slams once more.