The style of that! Hail to the Roman Empire!

Pretty horrible Latin, I'd say! The person who wrote this cares not a whit about syntax and cannot parse!

Et tu, Dennis?

The scary part is that I never learned Latin, but with only a quick knowledge of word roots, I actually understand this.

What I don't remember is which Julius actually conquered Britain.

Orange Julius is the one who conquered Britain, no?

I'm partial to this one. Loads more here and here

no caesar conquered Britain

It's not perfect, but the three trained Classicists in my apartment all laughed. We know how to take a joke without taking offense.

Here are a few of the problems:

After 'vince' in line two we need the vocative of Iulius, which is Julie ('Vince, Iulie, vince!).

Line three can be fixed in two ways: either make vide stand apart as it does in line one (Vide!), making the rest an independent sentence, or write 'Vide Iulium Britannos necare!' Your choice here depends upon whether you think the target audience of a Dick and Jane story is ready for the accusative-infinitive construction. (The first says, 'Look! Julius is killing the Brits! The second says 'See Julius kill the Brits!')

Morere is singular. The plural should be moritor, but I don't think it exists in any extant texts. The Romans, not having a horror or action film industry, had little reason to shout 'die' at masses of people, at least not in their texts.' And even then they might instead say something like, 'moriamini,' or 'moeriendum est vobis!'

Again, is the target audience ready for that? Or do we keep it simple at this stage even if it's not Ciceronian? Most grown-ups don't talk like the narrator of Dick and Jane stories, but no one shows outrage at the lack of advanced syntax there.

Rideo should take the accusative (Britannos). With a dative it's actually favorable ('smile upon' rather than 'laugh at').

You can quibble about a lot things but many corrections would violate the spirit of Dick and Jane style prose.

It is very funny though, especially the picture.