SpaceX's launch cadence is great for expanding their in-house constellation but basically irrelevant to companies purchasing rideshare slots for in orbit demonstrations like the Exploration Company. Take it from someone that's expecting to fly hardware on two of the next three Transporter missions (in late February and late June next year...). ArianeSpace could absolutely spin up an extra couple of missions on those timescales if their prices were the only option, and satellite integration timescales are a bigger issue for development than the timing of the next launch window. We wouldn't like Ariane 6 prices being added to our mission costs and at the margins some companies wouldn't afford it, but the Exploration Company has raised $230m and has already launched on an Ariane 6. The "Europeans have to use US capacity because they can't innovate
har har" argument simply isn't at all relevant to IODs on Transporter missions (which ironically are full of US companies buying slots on European companies' deployment platforms as well as having plenty of critical non-US kit even in SpaceX's unusually vertically-integrated supply chain. Not because the US can't innovate
har har but because the commercial space industry is globally distributed and price driven. Well, maybe not price driven if you're the military or Jeff Bezos building your LEO constellation on ArianeSpace launches whilst working on New Glenn...).
Don't think high cadence launches are even particularly high on the list of the US's military advantages in the event of global conflict extending into space: destruction of non-trivial amounts of orbital material would render its launch advantage moot until the Kessler syndrome problem was solved...