However some of the US services are so bad I can't believe they are actually right for July.
You're quite right; there were a number of cancellations in July and it's fair to assume not all pax would have been put on the same flight next day. However, it was inevitable that the introduction of new direct destinations by TCX and more capacity on JFK would lead to some erosion of traffic carried by UA and AA in particular. The questions were how much erosion and how would the US carriers react. I guess the jury is still out on both counts, and as LAX LHR, mentions, there's likely to be a state of flux for a while, conceivably with a bit of a shake-out eventually.
Not scientific I know, but seat plans suggested some loads were poor during the first 3 weeks of July but picked up when the school holidays started. From memory, August looked quite a lot better.
If there is destination 15 announced next week (see LAX LHR post 6404 above), it will be interesting to see what it is.