“whether genital warts can affect a woman’s ability to conceive.”
No. However, if she’s had warts she is at somewhat higher risk of having had other sexually transmitted infections including some (e.g., chlamydia, gonorrhoea) that can affect her ability to conceive.
“whether any medication might also affect one’s ability to become pregnant”
No. However, some treatments shouldn’t be used during pregnancy and, in general, if warts are judged to need treatment and pregnancy is planned, it’s best to treat the warts first and get pregnant after.
“whether treatment varies between countries (she’s American living in the US).”
Yes. Treatment even varies between doctors. There is not ideal treatment for genital warts. All we have are several imperfect treatments, each with its own advantages and disadvantages. However, in general, both U.S. and UK physicians tend to base their treatment recommendations on science and thus tend to use the same treatments.
“I believe they are hell to get rid”
Just like warts anywhere, they can come back after treatment and can be difficult to get rid of permanently. However, just like warts anywhere, they can also just disappear on their own.
“unprotected sex while they’re still present is not a good idea”
On the other hand, in a monagamous relationship, is it really smarter for one partner to try to avoid what is usually not a serious infection when (1) the means of prevention (condoms) is not 100% effective and (2) when the prophylactic measures may have to be used indefinitely (since you can’t be sure the wart virus is gone just because no warts are visible)?
“…anyone have any idea’s how a couple would deal with this situation given neither one of them ‘is getting any younger’ ?”
Ignore it?
For more than you want to know about the management of genital warts, you can go to http://www.evidence.org/, sign up for the free trial, and check out the chapter by Anna Wald on genital warts.