Research experience in the humanities is not as vital (or as typical) as in the sciences, but it never hurts your chances. Remember that you need to go well beyond the bare minimum to get accepted to a top PhD program. Most history departments accept only a dozen or so students a year; each department has several subfields, and they may accept only one medieval student in any given year (if any at all!). There will be students in the applicant pool who have very strong research backgrounds, especially if they’re coming from European (read: German) universities.
The most important aspects of your application are, in roughly descending order of importance, your statement of purpose, your writing sample, and your letters of recommendation. Undergraduate research is primarily helpful for your writing sample, as you’ll need 20-30 pages to send to each graduate program. It sounds like you’ll be able to send your junior paper or, depending on how fast you write, a chunk of your senior thesis, so you’re good to go there.
Your statement of purpose should be as precise as possible. It has to cover your research interests, your career goals, why you want to study at that university and with those professors, and what you bring to the table. This is another place undergraduate research comes in handy – it lets you figure out exactly what it is you want to study in graduate school. Try to narrow down the region(s), centuries, and historical approach (economic history? social history? political?) you’re most interested in. Even the most qualified applicant will be rejected if the professors think (s)he will not mesh well with their research interests.
To be blunt, yes. Foreign language experience is one of the first things used to cull applicants. You should have reading knowledge of at least one of them. Does your university offer a “French/German for reading” course? Failing that, you should plan to take either intro French or German next year.
I recommend applying to a mix of PhD and (funded) MA programs.
Your Latin background looks very good, and Spanish will be useful, I think. Your academic background otherwise looks very good, and being editor of a journal is certainly a bonus!