Easiest language for English native

I only speak English, I wish to learn another language.
The problem is that I've always kind of sucked at learning languages. I learnt some Indonesian, French and Japanese in school (Australian), and I was always terrible.
I understand that the more languages you learn, the easier it gets to learn more, is this true? What are the easiest languages to learn as an English speaker? Dutch and German?

Nobody is naturally good at learning languages, it's a skill you learn through doing.

Languages aren't easier to learn just because you already know more than 1 language, they're easier to learn because you learn _how_ to learn a language in the most efficient way for you.

If you want a useful language that's "easy" go with Norwegian, Icelandic, Swedish or Danish. Of course, their actual usefulness depends on what you plan to do with the language.

Don't fall into the trap of trying to learn a language for no reason other than learning the language itself (at least not for your first language -- once you get fluent in at least one or two non-native languages then you may be able to get by with just that for motivation) find a reason to learn it.