We can't focus ours to attack.
We can only send 50% out, part of it has to defend ships, part of it landing craft, part of it landing zones, part of it bombers.
Our air force will be very spread out to cover everything while the enemy can just wait for us to attack then intercept in minutes and use Radar to keep track plus it's AA.
Over enemy territory we're at a disadvantage.
Oh, not exactly. The point is not to gain all-out air superiority but local one for the duration of the campaign. Let's assume, for example, that they have an unspecified detection method of 30km range. [I am assuming that they have nor RADAR, and even if, that that's an acceptable maximum range]. This means they have about nine minutes from detection until our planes arrive over land. Maybe another ten to get to the target and bomb it, then another ten to retreat. Let's say 30 minutes total.
Now, this means that they have either nine to fifteen minutes to intercept the planes before the damage is done, or thirty to do so until after it's dropped. This means, for a higher speed than our planes, a distance of circa forty kilometres to intercept them - assuming the enemy planes are already in the air. So, whatever we're sending has to go up against all air patrols in a distance of forty kilometres plus closer fighters that are on alert. Since the enemy cannot keep all of its fighters in alert or in the air at once, this reduces the number of fighters they can dispatch for each threat. This may mean a reduction in numbers by 1/3 (8-hour patrols) * borderToPatrol/80km, so easily by one sixth, realistically far more.
We, on the other hand, can - for bombings at least, which were what I assumed for now, not landings - pretty easily concentrate half of our airforce on the escort in one attack, giving us a local air superiority of about three to one for a short time.
Of course, once we are over enemy territory, we have to deal with anti-aircraft guns. But, even our new 30mm gun has an effective service ceiling of 4km, while the sparrow can climb to seven. This means the main risk will be anti-aircraft artillery (something heavy, 80mm or so), which cannot hit more nimble fighters reliably. Hell, it can't even hit heavy bombers reliably.
Once invading, the whole thing looks differently, as we both have a single target needed to defend or attack, which means we both concentrate our airforces there. Then it's pretty much a fight for air superiority that we are disadvantaged in for our range.
Which it's doubtful we'll achieve and the enemy will up it's pruduction and refirect old production again soon as it did with the biwing.
So it might be necessary to actually do strategic bombing runs covered by fighters against their aircraft production factories.