The sooner the better. Spend the money with EU and UK defence manufacturers and give the boost to Europe's economy and not US. I'm sure the US firms will also be delighted with Trump if that happens.It's probably a year or 18 months away (that's a feeling, not evidence based) when a big day of reckoning comes and Europe pulls out of using US equipment.
It'll be a big shock, because it'll be a huge reduction in capability.
Quite what it'll do to the US - who knows.
Does feel like it'll be a massive human event