As far as the first field goal sealing the game, it's not true. You can't change a play like that, make it 10-3, and expect the entire game to follow exactly as it did. If it's 10-3, we kickoff, they don't get it from the spot of the miss. They could return the kickoff, they're going to run different plays, we're going to run different defenses. There probably is no interception. EVERYTHING from that point on would be different. We could have gone on to win 20-3, or lost 17-10. There are infinite possible outcomes. Sure it probably gives the team a better chance to win, but then again, it might not have.
Having said that...
This defense has to step it up at the end of the game when the other team is desparate. The Skins, Giants, and Seahawks games are inexusable. If it happens once it's one thing, but over and over is not OK. Yes, teams pass more when they need to score late in the game. Yes, the other team has 4 downs instead of 3. That doesn't mean the defense has to stop covering people. WRs have been wide open quite a bit in these 4th qtr. debacles. They need to do something about their pressure, and they need to tighten up their coverage. There is no reason this should happen this many times. If you can't stop a team when it matters, then what you do for the first 55 minutes doesn't matter.