When troops aren't on the ground but are in planes or ships, US ground troops aren't going to do much good. Those planes and ships need to make it to the US coastline without any loses in order for you to be correct on this one.
Even if we actually had a modern and up to date Navy and Air Force, that would not be a guarantee that all enemies could never land on our shores. And currently our Navy and Air Force are woefully obsolete.
And the invasion could well come from the north or south. It wouldn't have to be Mexico or Canada that invaded us either. Some aggressor country could invade them
to then use as a pathway to get to us.
The US has 10 carriers and over 50 attack submarines.
The submarines are a comfort. However, carriers will have only situational use against an advanced enemy. Launching medium-range bombers will extend their usefulness, but they really are yesterday's technology.
Who has more up to date destroyers than the US?
That I know of, France, Italy, the UK, and China.
The US airforce has 343 A10- Thunderbolts. The F-22 can't begin to match the ability of the A10 when it comes to supporting ground troops.
After all our A-10s are shot down because we didn't have enough F-22s to protect them, we'll have zero
It might be a small comfort to know that the enemy planes which will then be providing support to enemy troops will not be as advanced as our A-10s. But we'll still likely wish that we had protected our A-10s with F-22s.