A word of caution here. AFAIK, KL does not fly direct from PHL to AMS so presumably this is on AA, connecting onto BA. Gate closure time on BA is normally 20 minutes so the OP will in fact have 25 minutes to connect. BA flights to LCY often leave from the far end of the D PIer (around gates 24/25 typically although some leave from the D6 bus gate). A little bit of delay, a Polderbaan arrival, slow moving crowd to disembark, all of this can easily eat away at the available time. Not sure what the OP precise times are but I can't find a connection at exactly 45 mins at AMS between AA from PHL and BA to LCY.

I don't see AA offering that either, which would suggest that this is below the MCT.

I certainly would not risk it on separate tickets. If it is all on one ticket, then it does not really matter as BA would rebook the OP onto the next available service if the connection was missed. If it is not on the same ticket, the OP should be ready to have to buy a new ticket at walk-up fare if they miss the BA flight.