Probably no harm, but probably no benefit. At this age, the kids are learning phonetics, they are learning the inventory of different sounds. At a bit later age, they will no longer hear the sounds that are not in their language, same as adults.
In one interesting study, Kuhl’s team exposed 9 month old American
babies to Mandarin in various forms–in person interactions with native
Mandarin speakers vs. audiovisual or audio recordings of these
speakers–and then looked at the impact of this exposure on the babies’
ability to make Mandarin phonetic contrasts (not found in English) at
10-12 months of age. Strikingly, twelve laboratory visits featuring in
person interactions with the native Mandarin speakers were sufficient
to teach the American babies how to distinguish the Mandarin sounds as
well as Taiwanese babies of the same age. However, the same number
of lab visits featuring the audiovisual or audio recordings made no
impact. American babies exposed to Mandarin through these
technologies performed the same as a control group of American babies
exposed to native English speakers during their lab visits.
ref: http://eibalance.com/2013/05/03/kuhl-constructs-how-babies-form-foundations-for-language/
Now for older children, teenagers, I have heard anecdotal evidence from Icelanders I've met that if you grow up in a household with lots of English TV, some kids pick up English.
As for what to do instead, not enough space here. Suffice to say, teaching children a 2nd language can be done, and the challenges are often different from what people initially expect them to be.
And I think the jury is out on "flash card TV", some of the TV shows aimed at babies/toddlers is 1/2 step away from video flash cards. The key with any TV is that it be at their level (i.e. showing cartoons meant for 8 year olds to babies doesn't help them much).
Also, at this age, they are moving through linguistic milestones so rapidly, advice that works, might stop working a few months later.
