I just checked on Citymapper - the ultimate transportation app - for a Tuesday 5 PM, say for a 7 pm game, right. It's over 30 minutes from Paddington to Wembley for every option whether rail, tube, bus or some combo.

The best benefit of London's options over Bostons option (there's really only one) is that there's a rail/tube/bus option from all directions and times. And, they run regularly, while the MBTA will probably do 1 or 2 trips down and 1-2 trips back. So, while you're not waiting for the Foxboro train to arrive (because it'll be a special ticket time, not a commuter rail schedule), you have no options for winging it to get there extra early or stay extra late, as you would in London.

My overall point is that most football stadiums aren't in the "city." You're probably taking a train to the stadium from your hotel. MetLife near NYC isn't closer to NYC than Foxboro is to Boston. That's an hour+ trip by train out to a marshland if you stay in Midtown. (And if you stay outside, then you're taking the 30 minute train into NYC.) I think SoFi Stadium in LA is closer to the city, but public transport I don't know well.

However, if I was recommending a city to see WC 2026 and your team didn't matter - I'd choose Toronto. You can legit stay in Toronto and walk to the games and just about anyplace else a tourist wants in the city.