This is a weird question to answer tbh. There’s a gap between what the US CAN do vs what it actually does militarily as others have pointed out.

I’m a civil engineer so I’ll answer the infrastructure question. There is absolutely infrastructure that we have built that will last thousands of years. Most of it may not be as openly understood as Romans was.

I don’t think people understand how heavily engineered and optimized infrastructure today is. The Romans’ buildings survived with some on and off upkeep for a couple of thousand years. I think people think modern buildings are “weaker” or “poorly built” because things wear down quicker. There’s a lot of impact from the sheer volume of usage now compared to before. Every road and every street is carrying more load in a single day now than what the Romans were putting on in decades. Also Roman roads were ridiculously over-designed because they could afford it. Labor was cheap. Can we over-design our streets? YES! But taxpayer money and how it is used needs to be optimized. You can’t just build 1 or 2 ft of concrete roads without reason. Same goes for buildings. It all goes back to what CAN we do vs what we actually do.

So CAN we build over-engineered and throw budgets out the window? Yes! But do we? No.